Silicon is present in interstellar dust grains, meteorites and asteroids, and to date thirteen silicon-bearing molecules have been detected in the gas-phase towards late-type stars or molecular clouds, including silane and silane derivatives. In this work, we have experimentally studied the interaction between atomic silicon and hydrogen under physical conditions mimicking those at the atmosphere of evolved stars. We have found that the chemistry of Si, H and H2 efficiently produces silane (SiH4), disilane (Si2H6) and amorphous hydrogenated silicon (a-SiH) grains. Silane has been definitely detected towards the carbon-rich star IRC+10216, while disilane has not been detected in space yet. Thus, based on our results, we propose that gas-phase reactions of atomic Si with H and H2 are a plausible source of silane in C-rich AGBs, although its contribution to the total SiH4 abundance may be low in comparison with the suggested formation route by catalytic reactions on the surface of dust grains. In addition, the produced a-SiH dust analogs decompose into SiH4 and Si2H6 at temperatures above 500 K, suggesting an additional mechanism of formation of these species in envelopes around evolved stars. We have also found that the exposure of these dust analogs to water vapor leads to the incorporation of oxygen into Si-O-Si and Si-OH groups at the expense of SiH moieties, which implies that, if this type of grains are present in the interstellar medium, they will be probably processed into silicates through the interaction with water ices covering the surface of dust grains.S-methyl thioformate CHSC(O)H is a monosulfur derivative of methyl formate, a relatively abundant component of the interstellar medium (ISM). S-methyl thioformate being, thermodynamically, the most stable isomer, it can be reasonably proposed for detection in the ISM.
This work aims to experimentally study and theoretically analyze the ground and first torsional excited states for CHSC(O)H in a large spectral range for astrophysical use.
S-methyl thioformate was synthesized as a result of a reaction of methyl mercaptan with acetic-formic anhydride. The millimeter-wave spectrum was then recorded for the first time from 150 to 660 GHz with the solid-state spectrometer located at Lille.
A set of 3545 lines is determined and combined with 54 previously measured lines in the microwave region, belonging to ground state = 0 as well as 1391 transitions in the first excited state of torsion = 1. Some 164 lines were also assigned to = 2 for the A-species. A global fit was performed using the BELGI-Ccode taking into account the large splitting of A and E lines due to methyl internal rotation motion with a relatively low barrier, V= 127.4846(15) cm.
Using our spectroscopy work, a deep search of S-methyl thioformate was carried out in the IRAM 30m and ALMA data of different high-mass star-forming regions (Orion KL and Sgr B2). We derived an upper limit to the CHSC(O)H column density in these regions.
Using our spectroscopy work, a deep search of S-methyl thioformate was carried out in the IRAM 30m and ALMA data of different high-mass star-forming regions (Orion KL and Sgr B2). We derived an upper limit to the CH3SC(O)H column density in these regions.Cyanoacetamide is a -CN bearing molecule that is also an amide derivative target molecule in the interstellar medium.
The aim of our investigation is to analyze the feasibility of a plausible formation process of protonated cyanoacetamide under interstellar conditions and to provide direct experimental frequencies of the ground vibrational state of the neutral form in the microwave region in order to enable its eventual identification in the interstellar medium.
We used high-level theoretical computations to study the formation process of protonated cyanoacetamide. Furthermore, we employed a high-resolution laser-ablation molecular beam Fourier transform spectroscopic technique to measure the frequencies of the neutral form.
We report the first rotational characterization of cyanoacetamide, and a precise set of the relevant rotational spectroscopic constants have been determined as a first step to identifying the molecule in the interstellar medium. We fully explored the potential energy surface to study a gas-phase reaction on the formation process of protonated cyanoacetamide. We found that an exothermic process with no net activation barrier is initiated by the high-energy isomer of protonated hydroxylamine, which leads to protonated cyanoacetamide.
We report the first rotational characterization of cyanoacetamide, and a precise set of the relevant rotational spectroscopic constants have been determined as a first step to identifying the molecule in the interstellar medium. We fully explored the potential energy surface to study a gas-phase reaction on the formation process of protonated cyanoacetamide. We found that an exothermic process with no net activation barrier is initiated by the high-energy isomer of protonated hydroxylamine, which leads to protonated cyanoacetamide.Mitochondria are cellular organelles responsible for generation of chemical energy in the process called oxidative phosphorylation. They originate from a bacterial ancestor and maintain their own genome, which is expressed by designated, mitochondrial transcription and translation machineries that differ from those operating for nuclear gene expression. In particular, the mitochondrial protein synthesis machinery is structurally and functionally very different from that governing eukaryotic, cytosolic translation. Despite harbouring their own genetic information, mitochondria are far from being independent of the rest of the cell and, conversely, cellular fitness is closely linked to mitochondrial function. Mitochondria depend heavily on the import of nuclear-encoded proteins for gene expression and function, and hence engage in extensive inter-compartmental crosstalk to regulate their proteome. https://www.selleckchem.com/products/sitagliptin.html This connectivity allows mitochondria to adapt to changes in cellular conditions and also mediates responses to stress and mitochondrial dysfunction. With a focus on mammals and yeast, we review fundamental insights that have been made into the biogenesis, architecture and mechanisms of the mitochondrial translation apparatus in the past years owing to the emergence of numerous near-atomic structures and a considerable amount of biochemical work. Moreover, we discuss how cellular mitochondrial protein expression is regulated, including aspects of mRNA and tRNA maturation and stability, roles of auxiliary factors, such as translation regulators, that adapt mitochondrial translation rates, and the importance of inter-compartmental crosstalk with nuclear gene expression and cytosolic translation and how it enables integration of mitochondrial translation into the cellular context.